Molecular phylogeny of the stress-70 protein family with reference to algal relationships

The stress-70 protein family has previously been shown to be a useful tool for molecular phylogeny at the kingdom to family levels. Although sequences of many members of the stress-70 family are available, few genes from the Protoctista have been sequenced to date. Phylogenetic analyses of algae based on various molecules have not, as yet, provided dear results concerning relationships between major divisions. We cloned and sequenced several algal stress-70 genes in order to provide additional data and to further analyse phylogenetic relationships among algal divisions. New nuclear sequences were obtained from Guillardia theta (Cryptophyta), Ascophyllum nodosum (Heterokontophyta) and Cyanophora paradoxa (Glaucocystophyta). Phylogenetic trees of the stress-70 protein family calculated using different methods are presented. In our trees, the heterokont alga Ascophyllum nodosum is closely related to the slime mould Dictyostelium discoideum, while the nucleomorph (eukaryotic endosymbiont) of the cryptophyte Rhodomonas salina seems to be related to the chlorobiont lineage. The glaucocystophyte Cyanophora paradoxa and the nuclear sequence (host) of the cryptomonad alga Guillardia theta also seem to be closely related. The Cryptophyta and the heterokont algae have evolved from different secondary endosymbiotic events involving different hosts and probably different endosymbionts. However, until more stress-70 sequences of algal divisions become available no definitive conclusions can be drawn concerning branching of the major divisions

Arabidopsis GERANYLGERANYL DIPHOSPHATE SYNTHASE 11 is a hub isozyme required for the production of most photosynthesis-related isoprenoids

Most plastid isoprenoids, including photosynthesis-related metabolites such as carotenoids and the side chain of chlorophylls, tocopherols (vitamin E), phylloquinones (vitamin K), and plastoquinones, derive from geranylgeranyl diphosphate (GGPP) synthesized by GGPP synthase (GGPPS) enzymes. Seven out of 10 functional GGPPS isozymes in Arabidopsis thaliana reside in plastids. We aimed to address the function of different GGPPS paralogues for plastid isoprenoid biosynthesis. We constructed a gene co-expression network (GCN) using GGPPS paralogues as guide genes and genes from the upstream and downstream pathways as query genes. Furthermore, knock-out and/or knock-down ggpps mutants were generated and their growth and metabolic phenotypes were analyzed. Also, interacting protein partners of GGPPS11 were searched for. Our data showed that GGPPS11, encoding the only plastid isozyme essential for plant development, functions as a hub gene among GGPPS paralogues and is required for the production of all major groups of plastid isoprenoids. Furthermore, we showed that the GGPPS11 protein physically interacts with enzymes that use GGPP for the production of carotenoids, chlorophylls, tocopherols, phylloquinone, and plastoquinone. GGPPS11 is a hub isozyme required for the production of most photosynthesis-related isoprenoids. Both gene co-expression and protein-protein interaction likely contribute to the channeling of GGPP by GGPPS11